Because it's easy and -- until somebody calls us on it -- fun. We Canadians in particular love to feel superior to our bigger, richer, stronger neighbours, and the making of snarky remarks is the only field in which we consistently outstrip them.

If I had a nickel for every anecdote I've heard about dumb American tourists (e.g., the ski-bearing car on Wellington Street in August), I could buy a round of pints for the entire membership of the Mudcat Cafe.